This invention relates to butterfly valves of the type possessing a function of establishing tight shut and preventing itself from developing erosion as a matter of course, and enabling even a minute flow volume to be duly adjusted particularly in the area of small degree of opening or the area of minute degree of opening and exhibiting a prominent effect in high range ability.
Butterfly valves, on account of distinctions, such as simplicity of structure, lightness and low operating force, are being used as stop valves or, depending on purposes of application, as flow volume adjusting valves. Particularly when such a butterfly valve is used as a flow volume adjusting valve, it has the possibility of not only generating cavitation on the downstream side of the valve member to emit vibration and noise but also inducing the so-called erosion, namely the phenomenon of the valve member and the adjunct piping yielding to damage and corrosion.
With the object of solving these problems, various countermeasures have been proposed.
JP-A SHO 57-157866, for example, discloses a method for repressing the cavitation which would occur on the downstream side of the valve member by providing the outer peripheral edge of the valve member with spaced projections resembling the teeth of a comb and causing the projections to transform a fluid into a jet. JUM-A SHO 62-6568 discloses a method for rectifying the turbulence of a fluid by providing the opposite outer peripheral parts of a valve member each with a belt member and forming a group of numerous small holes in each of the belt members. JP-B HEI 05-78713 or JUM-A HEI 05-8139 teaches a means for preventing the cavitation by fitting the valve member on the secondary side thereof with a rectifying plate. JUM-C 2589805 concerns a butterfly valve which is intended to repress the cavitation by fitting an eccentrically shaped valve member on one side thereof with a wing member and forming a multiplicity of small holes in the wing member, and JUM-B HEI 07-43553 concerns a butterfly valve which is intended to repress the cavitation by forming small through holes in circular flanges on the opposite sides of a valve member. JP-A HEI 07-208615 also concerns a valve which is intended to repress the cavitation by forming small holes in each of the laterally opposite wing members of a valve member.
Since the conventional methods cited above invariably have as their main objects the attainment of the prevention of the cavitation by rectifying the flow of a fluid, they are substantially incapable of either effecting fine adjustment of a fluid in the area of low degree of opening or the area of minute degree of opening or offering a fully satisfactory control valve for the adjustment of a flow volume in the area of low degree of opening or the area of minute degree of opening. Thus, a practicable butterfly valve possessed of an efficient performance of high range ability has not been realized to date. Such is the actual state of affairs.
The butterfly valves of the type intended for use in air conditioners, for example, are used in a fully opened state in the summer season which demands full use of the air conditioners, whereas they are generally used as retained in the area of low degree of opening or the area of minute degree of opening which falls in the range of adjustment of not more than 40% of the degree of opening in the other seasons. Depending on the purpose of use, the valves of this type are used frequently for controlling the fluid in the area of low degree of opening or the area of minute degree of opening.
Particularly, many of these butterfly valves are used in a state having their valve seats fitted with an annular rubber seat. When they are used in the area of low degree of opening or the area of minute degree of opening, the volumetric flow rate of the fluid is increased because the flow path between the valve member and the rubber seat is narrowed and this increased volumetric flow rate possibly induces the rubber seat to succumb to the so-called phenomenon of erosion.
This invention has been developed for the purpose of solving the various problems encountered by the conventional butterfly valves and has for the object thereof the provision of a butterfly valve which possesses a function of resisting cavitation, prevents occurrence of erosion as a matter of course, permits fine adjustment of the fluid in the valve in the area of minute degree of opening or the area of low degree of opening, manifests a high range ability, and excels in the function of control and the function of tight shut.
To attain the above object, the present invention provides a butterfly valve for opening and shutting an interior of an elastic seat ring mounted in a cylindrical valve casing by rotation of a disc valve member, wherein the butterfly valve comprises a depressing valve part formed at least on a side of an orifice of the valve member and adapted to make depressing contact with the elastic seat ring in an area of low degree of valve opening or in an area of minute degree of valve opening, a void part formed along an outer peripheral edge of the valve member or at a position of a downstream side of the outer peripheral edge, and a communicating part formed in the valve member or depressing valve part and adapted to form communication from an interior of the void part toward the downstream side.
The butterfly valve further comprises tight-shut valve shutting parts formed along the outer peripheral edge of the valve member and including a valve shutting part disposed on the orifice side, and a site of an increased wall thickness of the valve member between the valve shutting part and the depressing valve part, wherein the depressing valve part is formed as directed toward the downstream side of the valve shutting part, the void part is disposed at the site of the increased wall thickness, and the communicating part is intended for effecting fluid control.
In the first-mentioned butterfly valve, the depressing valve part is formed in a smaller diameter than the valve member in order that the depressing valve part may exert a smaller amount of depression on the seat ring than the valve member on the seat ring.
In the first-mentioned butterfly valve, the depressing valve part at least on the orifice side has formed therein an inflow part for admitting a fluid from an outer peripheral surface of the depressing valve part toward the downstream side of the valve member and controlling a volumetric flow rate of the fluid.
In the first-mentioned butterfly valve, the depressing valve part comprises wing-like pieces formed along opposite outer peripheral edges of the valve member as directed toward a direction of shutting the valve member and the wing-like pieces have outer peripheral surfaces thereof formed spherically.
A butterfly valve for opening and shutting an interior of an elastic seat ring mounted in a cylindrical valve casing by rotation of a disc valve member, characterized in that a fluid is allowed not to flow from a nozzle side of the valve member but to flow only from an orifice side thereof to attain high range ability.
In the butterfly valve, an outer peripheral edge of the valve member is provided on a nozzle side and an orifice side with depressing valve parts formed as directed toward a downstream side and the depressing valve part on the orifice side has formed therein an inflow part for admitting the fluid from an outer peripheral surface of the depressing valve part toward the downstream side and adjusting a volumetric flow rate of an incoming fluid.
A butterfly valve for opening and shutting an interior of an elastic seat ring mounted in a cylindrical valve casing by rotation of a disc valve member, wherein the butterfly valve comprises a depressing valve part provided along an outer peripheral edge on an orifice side of the valve member as directed toward a downstream side and an inflow part formed in a neighborhood of the depressing valve part for opening toward a secondary side to enable adjustment of a volumetric flow rate of a fluid to be attained with high accuracy in an area of minute degree of valve opening.
A butterfly valve for opening and shutting an interior of an elastic seat ring mounted in a cylindrical valve casing by rotation of a disc valve member, wherein the valve member is provided along an outer peripheral edge on a nozzle side and an orifice-side outer peripheral edge with wing-like pieces directed toward a downstream side, with lengths of the wing-like pieces on the nozzle side and the orifice side varied to suppress a phenomenon of jumping during break-off of a largest movable part of the valve member from the elastic seat ring.